Implantable medical devices are used for a variety of applications, which may include one or both of patient sensing and therapy delivery. For example, implantable medical devices are used to deliver therapy to patients to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson's disease, multiple sclerosis, spinal cord injury, cerebral palsy, amyotrophic lateral sclerosis, dystonia, torticollis, epilepsy, pelvic floor disorders, gastroparesis, cardiac arrhythmia, or obesity. Some implantable medical devices deliver electrical stimulation in the form of electrical pulses or substantially continuous signals, via one or more leads that include electrodes located proximate to a target therapy delivery site. Some implantable medical devices chronically deliver metered dosages of a therapeutic agent, such as pharmaceutical agents, insulin, pain relieving agents, gene therapy agents, or the like, to a target therapy delivery site via a catheter. The target therapy delivery site may be, for example, a nerve or other tissue site, such as a spinal cord, pelvic nerve, pudendal nerve, stomach, bladder, or within a brain or other organ of a patient, or within a muscle or muscle group of a patient. In some embodiments, multiple therapy types, e.g., electrical stimulation and therapeutic agent delivery, may be used simultaneously to deliver optimal and efficient therapy to a patient.
Some implantable medical devices are used for patient sensing or monitoring alone, while others provide sensing in addition to therapy. Some implantable medical devices deliver therapy based on or in response to one or more sensed physiological parameters of a patient. Examples of physiological parameters that may be monitored include activity level or movement, posture, pressure, temperature, the concentration of one or more substances within the patient such as glucose, electrical activity of the brain such an encephalogram (EEG), electrical activity of the heart such as an electrocardiogram (ECG), or muscle activity such as an electromyogram (EMG). Sensors used to detect physiological parameters include accelerometers, thermistors, capacitive sensor, optical sensors and electrodes, which in some cases may also be used for delivery of electrical stimulation.
In order for an implantable medical device to continue to provide effective therapy and/or monitoring, each of the elements or components of the implantable medical device, or a system including the implantable medical device, must continue to operate as expected. In some cases, in order to ensure or verify effective operation, integrity tests are performed on various elements of an implantable medical device system. For example, lead integrity tests have been performed on implantable leads carrying electrodes for delivery of electrical stimulation and sensing by an implantable medical device.
Typically, such integrity tests have been performed manually, by a clinician, during a follow-up visit with the patient. However, integrity tests performed only at follow-up visits may detect a component failure too late, or fail to detect an intermittent problem, such as an intermittent lead fracture. This may leave the patient without appropriate therapy or sensing for a period of time away from the clinic.
It has also been proposed to automatically perform integrity tests at regular, periodic intervals, e.g., once per day, when the patient is away from the clinic. However, regular integrity tests consume a significant amount of power from a power source of the implantable medical device. Furthermore, such regular integrity tests may still fail to detect an intermittent problem which does not manifest during the test.